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Mitiglinide belongs to the meglitinide class of blood glucose-lowering drugs and is currently co-marketed in Japan by Kissei and Takeda. The North America rights to mitiglinide are held by Elixir Pharmaceuticals. Mitiglinide has not yet gained FDA approval.

Mitiglinide calcium hydrate was approved by Pharmaceuticals and Medical Devices Agency of Japan (PMDA) on January 29, 2004. It was co-developed and co-marketed as Glufast® by Takeda and Kissei in Japan.

Mitiglinide is a rapid-acting insulin secretion-stimulating agent. It stimulates insulin secretion by closing the ATP-sensitive K+ (ATP) channels in pancreatic beta-cells. It is indicated for the treatment of type 2 diabetes mellitus.

Glufast® is available as tablet for oral use, containing 5 mg or 10 mg of Mitiglinide calcium hydrate. The recommended dose is 10 mg three times daily just before each meal (within 5 minutes).

Mitiglinide calcium hydrate

The condensation of dimethyl succinate (I) with benzaldehyde (II) by means of NaOMe in refluxing methanol followed by hydrolysis with NaOH in methanol/water gives 2-benzylidenesuccinic acid (III). Compound (III) is treated with refluxing Ac2O, yielding the corresponding anhydride (IV), which by reaction with cis-perhydroisoindole (V) in toluene affords the monoamide (VI). This amide is reduced with H2 over a chiral Rhodium catalyst and treated with (R)-1-phenylethylamine (VII) to provide the chiral salt (VIII) as a single diastereomer isolated by crystallization. Finally, this salt is treated first with aqueous NH4OH and then with aqueous CaCl2.

he optical resolution of racemic 2-benzylsuccinic acid (XV) using the chiral amines (R)-1-phenylethylamine (VII), (R)-1-(1-naphthyl)ethylamine (XIV) or (S)-1-phenyl-2-(4-tolyl)ethylamine (XVI) is carried out by fractional crystallization of the corresponding diastereomeric salts and treatment with 2N HCl, providing the desired enantiomer 2(S)-benzylsuccinic acid (XVII). Reaction of (XVII) with SOCl2 gives the corresponding acyl chloride (XVIII), which is treated with 4-nitrophenol (XIX) and TEA in dichloromethane to yield the activated diester (XX). The regioselective reaction of (XX) with cis-perhydroisoindole (V) in dichloromethane affords the monoamide (XXI), which by reaction with HCl and methanol provides the corresponding methyl ester (XXII). This ester is hydrolyzed with NaOH to the previously described chiral succinamic acid (XIII), which is finally converted into its calcium salt.

Perhydroisoindole derivative, (S)-mitiglinide of formula I is a potassium channel antagonist for the treatment of type 2 diabetes mellitus and is chemically known as (5)-2-benzyl-3-(cis-hexahydro-2- isoindolinylcarbonyl) propionic acid.

Formula I

It has potent oral hypoglycemic activity and is structurally different from the sulphonylureas, although it stimulates calcium influx by binding to the sulphonylurea receptor on pancreatic β-cells and closing K+ATP channels. Perhydroisoindole derivatives including (S)-mitiglinide and salts thereof were first disclosed in US patent 5,202,335. This patent discloses preparation of (S)-mitiglinide by the reaction of (5)-3-benzyloxycarbonyl-4-phenylbutyric acid with cis-hexahydroisoindoline in the presence of N- methylmorpholine and isobutyl chloroformate followed by debenzylation with palladium on carbon in ethyl acetate to yield (5)-mitiglinide as viscous oil. (S)-Mitiglinide is isolated as its hemi calcium salt using calcium chloride in water which is further recrystallized with diisopropyl ether. Melting point of calcium salt of mitiglinide calcium dihydrate salt is herein reported as 179-185 0C. (S)-Mitiglinide prepared by the above process is obtained in low yields. Further, the synthetic method described in the patent does not enable the desired regioselectivity. Extensive purification steps are required to obtain the desired compound, which makes the process unattractive from industrial point of view. US patent 6,133,454 discloses a process for the preparation of (S)-mitiglinide by reacting dimethyl succinate with benzaldehyde in methanolic medium, to yield a diacid which is converted to corresponding anhydride and is further reacted with the perhydroisoindole to yield 2-[(cis- perhydroisomdol^-ytycarbonylmethyl^-phenylacrylic acid which is then subjected to catalytic hydrogenation using the complex rhodium/(2S,4S)-N-butoxycarbonyl-4-diphenylphosphino-2-diphenyl- phosphino-methylpyrrolidine (Rh/(S,S) BPPM) as asymmetric hydrogenation catalyst, followed by conversion to pharmaceutically acceptable salt of (S)-mitiglinide. The above patent utilizes ruthenium complex which is expensive, carcinogenic and toxicity, hence not recommended for industrial scale. European patent publication no. EP 0967204 discloses the preparation of mitiglinide by deprotecting benzyl-(S)-2-benzyl-3-(cis-hexahydro-2-isoindolinyl-carbonyl) propionate and converting the same to calcium dihydrate salt in crystalline form using calcium chloride, water and ethanol. The crystals of calcium salt are further recrystallized using ethanol and water. But the patent is silent about the crystalline form of mitiglinide calcium.

It will be appreciated by those skilled in the art that perhydroisoindole derivative, (S)-mitiglinide of formula I contains a chiral centre and therefore exists as enantiomers. Optically active compounds have increasingly gained importance since the technologies to develop optically active compounds in high purity have considerably improved. Obtaining asymmetric molecules has traditionally involved resolving the desired molecule from a racemic mixture using a chiral reagent, which is not profitable as it increases the cost and processing time. Alternatively, desired enantiomer can be obtained by selective recrystallization of one enantiomer. However such a process is considered inefficient, in that product recovery is often low, purity is uncertain and more than 50% of the material is lost. Enantiomers can also be resolved chromatographically, although the large amount of solvent required for conventional batch chromatography is cost prohibitive and results in the preparation of relatively dilute products. Limited throughput volumes also often make batch chromatography impractical for large-scale production. Even so, it is a common experience for those skilled in the art to find chiral separation of certain chiral mixtures to be inefficient or ineffective, thereby resulting in the efforts towards development of newer methodologies for asymmetric synthesis.

It would be of significant advantage to obtain (.S)-mitiglinide by development of reaction conditions necessary for productive manufacture of the required (5)-enantiomer, substantially free of the unwanted (R)-enantiomer, in large quantities that meet acceptable pharmaceutical standards. It is the property of the solid compounds to exist in different polymorphic form. By the term polymorphs mean to include different physical forms, crystal forms, crystalline/liquid crystalline/non-crystalline (amorphous) forms. This has especially become very interesting after observing that many antibiotics, antibacterials, tranquilizers etc, exhibit polymorphism and some/one of the polymorphic forms of a given drug exhibit superior bio-availability and consequently show much higher activity compared to other polymorphs. It has also been disclosed that the amorphous forms in a number of drugs exhibit different dissolution characteristics and in some cases different bioavailability patterns compared to the crystalline form [Konne T., Chem. Pharm. Bull. 38, 2003 (1990)]. The solubility of a material is also influenced by its solid-state properties, and it has been suggested that the solubility of an amorphous compound is 10 to 1600 times higher than that of its most stable crystalline structures (Bruno C. Hancock and Michael Parks, ‘What is the true solubility advantage for amorphous pharmaceuticals’, Pharmaceutical Research 2000, Apr; 17(4):397-404). Thus it can be concluded that amorphous products are in general more soluble and often show improved absorption in humans.

Thus, there is a widely recognized need for developing a stable polymorph, which would further offer advantages over crystalline forms in terms of better dissolution and the availability profiles. Also none of the prior art references disclose amorphous form of mitiglinide calcium. Thus present invention provides amorphous form of mitiglinide calcium.

It is also required that the final API like mitiglinide whether in the amorphous form or crystalline form must be free from the other impurities including the unwanted enantiomer, these can be side product and by product of the reaction, degradation products and starting materials. Impurities in final API are undesirable and in extreme cases, might even be harmful to a patient being treated with a dosage form containing the API. Therefore impurities introduced during commercial manufacturing processes must be limited to very small amounts and are preferably substantially absent. These limits are less than about 0.15 percent by weight of each identified impurity and 0.10 % by weight of unidentified and/or uncharacterized impurities. After the manufacture of APIs, the purity of the products, such as (S)- mitiglinide calcium dihydrate is required before commercialization, and in the manufacture of formulated pharmaceuticals. Therefore, pharmaceutical active compounds must be either free from these impurities or contain the impurities in acceptable limits. There is also a need for the isolation, characterization and identification of the impurities and their use as reference markers and reference standard. Thus, the present invention meets the need in the art for a novel, efficient and industrially advantageous process for providing optically pure perhydroisoindole derivatives, particularly (iS)-mitiglinide, which is unique with respect to its simplicity, scalability and involves controlling the steps of the reaction so that predominantly the desired (S)-enantiomer is produced in high yields and purity. The present invention also provides substantially pure (S)-mitiglinide and salts thereof having novel amide impurity in acceptable limit or free from this impurity.

Example 1: Preparation of (R) 4-benzyl-3-(3-phenylpropionv0-oxazolidin-2-one To a solution of (R)-4-benzyloxazolidin-2-one (50 g), 4-dimethylaminopyridine (4.85 g), 3-phenyl propionic acid (55.08 g) in dichloromethane (375 ml) under nitrogen atmosphere at 0-5 0C, dicyclohexylcarbodiimide (975.65 g) was added. The temperature was slowly raised to 25-30 0C and stirring was continued until no starting material was left as was confirmed by thin layer chromatography. Dicyclohexylurea formed during the reaction was filtered, washed with dichloromethane (200 ml) and the filtrate was washed with saturated solution of sodium bicarbonate (500 ml). The solution was dried over sodium sulphate and solvent was distilled off to obtained crude product which was purified from methanol (200 ml) at 10-15 °C and washed with methanol (50 ml) to obtain 81.0 g of the title compound. Example 2: Preparation of 3(5)-benzyl-4-(4-(J?)-benzyl-2-oxo-oxazolidin-3-yl)-4-oxo-butyrϊc acid tert-butyl ester

To a solution of (/?)-4-benzyl-3-(3-phenyl-propionyl)-oxazolidin-2-one (150 g) in anhydrous tetrahydrofuran (1.5 It) was added a solution of sodium hexamethyldisilazane (462 ml, 36-38% solution in tetrahydrofuran) with stirring at -85 to -95 0C for 60 minutes. Tert-butyl bromo acetate (137.5 g) in tetrahydrofuran (300 ml) was added to reaction mass and then stirred to 60 minutes at -85 to -95 0C. After completion of the reaction (monitored by TLC), the reaction mixture was poured into ammonium chloride solution (10%, 2.0 It) and extracted with ethyl acetate (2×750 ml). The combined organic layer was washed with demineralized water (1×750 ml) and dried over sodium sulphate. The solvent was evaporated under reduced pressure to obtain oily residue which was stirred with mixture of n-hexane (100 ml) and isopropyl alcohol (100 ml) at Oto -50C, filtered and dried under vacuum to obtain 153.12 g of title compound having chemical purity 99.41%, chiral purity 99.91% by HPLC, [α]D20: (-)97.52° (c = 1, CHCl3) and M.P. : 117.1-118.20C.

Example 3: Preparation of 3(5)-benzyl-4-(4(i?)-benzyl-2-oxo-oxazolidin-3-yl)-4-oxobutyric acid Trifluoroacetic acid (100 g) was added to a solution of 3(5)-benzyl-4-(4-(/?)-benzyl-2-oxo-oxazolidin-3- yl)-4-oxobutyric acid tert-butyl ester (100 g) in dichloromethane (700 ml) at 25 0C and mixture was stirred further for about 12 hours ( when TLC indicated reaction to be complete). The reaction mixture was poured in to ammonium chloride solution (10%, 500 ml). The dichloromethane layer was separated and aqueous layer was extracted with dichloromethane (2 x 250 ml). The combined organic layer was dried over sodium sulphate and evaporated under reduced pressure to obtain title compound. The crude product was recrystallized from a mixture of ethyl acetate: n-hexane (1:4, 500 ml) to obtain 78.75g of the title compound having purity 99.56% by HPLC and M.P.: 145.9-146.40C.

To a solution of 3(5)-benzyl-4-(4-(/?)-benzyl-2-oxo-oxazolidin-3-yl)-4-oxo-butyric acid (50 g) in anhydrous dichloromethane (1.25 It) was added triethylamine (50 ml) with stirring at -20 to -30 0C and the stirred for 15 minutes. A solution of isobutylchloroformate (37.50g) in anhydrous dichloromethane (50 ml) was added at -20 to -30 0C and stirred for 60 minutes. Thereafter, a solution of cis- hexahydroisoindoline (32.50 g) in anhydrous dichloromethane (50 ml) was slowly added by maintaining temperature -20 to -300C. After the completion of the reaction (monitored by HPLC), the mixture was successively washed with 0.5N hydrochloric acid solution (500 ml), brine (300 ml) and dried over sodium sulphate. The solvent was evaporated under reduced pressure to obtain 102.0 g of the title compound having purity 94.39% by HPLC.

To the crude (2S)-2-benzyl-l-((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)- butane- 1,4-dione (51.0 g) was added methanol (150 ml) and the mixture was stirred for 5 hours at 0 to 5 0C. Solid that precipitated out was filtered, slurry washed with cold methanol (25 ml) and dried at 45 -50 0C under vacuum to obtain 28.80 g of pure title compound as a crystalline solid having purity of 99.71% by HPLC and M. P.: 104.1-105.70C.

(2S)-2-Benzyl- 1 -((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)-butane- 1 ,4-dione (28.0 g) was dissolved in tetrahydrofuran (196 ml) and a mixture of lithium hydroxide monohydrate (3.51 g) in demineralized water (56 ml) and hydrogen peroxide (40% solution, 5.5 ml) was added with stirring at 0 to 5 0C over a period of 30 minutes. The reaction mixture was further stirred at 0 to 5 0C till the completion of the reaction. After the completion of the reaction (monitored by TLC), the reaction was quenched with the addition of cooled sodium meta-bisulphate solution (25%, 168 ml) at 0 to 10 0C. The reaction mixture was extracted with ethyl acetate (2×112 ml), the layers were separated and the aqueous layer was discarded. The HPLC analysis of the aqueous layer shows 0.77% of amide impurity. The ethyl acetate layer was then extracted with aqueous ammonia solution (4%, 2×40 ml). The layers were separated and the aqueous layer was further extracted with ethyl acetate (2×280 ml). Combined ethyl acetate layer was discarded. This aqueous layer (280 ml) was used as such in the next stage. The aqueous layer display purity 96.19 % by HPLC and amide impurity 0.04% by HPLC. Step-2: Preparation of calcium salt of dSVmitiglinide

To the above stirred solution of (S)-mitiglinide in water and ammonia(280 ml), methanol (168 ml) was added, followed by calcium chloride (4.48 g) dissolved in demineralized water (56 ml) at ambient temperature and the mixture was stirred for 2 hours. The resulting precipitate was filtered, successively slurry washed with water (3 x 140 ml) and acetone (2 x 70 ml) and dried at 450C -500C under vacuum to obtain 16.1 g of title compound having purity 99.67% by HPLC and amide impurity 0.01% by HPLC. The title product was re-precipitated from a mixture of methanol and water and dried to obtain pure title compound.

Example 7: Preparation of (.SVmitiglinide

To a solution of (2S)-2-benzyl-l-((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)- butane- 1,4-dione (50 g) in tetrahydrofuran (350 ml) was added a solution of lithium hydroxide monohydrate (8.65 g) in demineralized water (100 ml) and hydrogen peroxide (30% w/w, 40 ml) with stirring at 5 to 10 0C over a period of 15 minutes. After the completion of reaction, sodium meta- bisulphate solution (40%, 500 ml) was added to the reaction mixture and the mixture was extracted with ethyl acetate (2 x 250 ml). The organic layer was dried over sodium sulphate and evaporated under vacuum to obtain 45.5 g of title compound having 35 % of R-benzyl oxozolidin-2-one as impurity. Example 8: Purification of (.S)-mitiglinide

Aqueous ammonia solution (4%, 300 ml) was added to the crude (5)-mitiglinide (30 g) and stirred. The reaction mixture was washed with ethyl acetate (3 x 300 ml). Thereafter the reaction mixture was acidified to pH 1 to 2 with IN hydrochloric acid solution (250 ml) and extracted with ethyl acetate (2 x 150 ml). The layers were separated and ethyl acetate layer was washed with demineralized water (2 x 150 ml), dried over sodium sulphate and then evaporated under reduced pressure to obtain 16.2 g of pure (5)-mitiglinide having purity 95.55% by HPLC Example 9: Preparation of calcium salt of (S)-mitiglinide

To a solution of (<S)-mitiglinide (15 g) in water (150 ml) and aqueous ammonia solution (25%, 15 ml) at 25 to 30 0C, a solution of calcium chloride (7.5 g) in demineralized water (37.5 ml) was added. The mixture was stirred for 1 hour to precipitate the calcium salt of (5)-mitiglinide dihydrate. The resulting precipitate was filtered, slurry washed with water (3 x 150ml) and dried at 45 to 50 0C to obtain 13.25 g of the title compound having purity of 98.84% by HPLC. Example 10: Purification of calcium salt of (5)-mitiglinide

(iS)-mitiglinide calcium (10 g) was dissolved in dimethylformamide (100 ml). This is followed by the addition of demineralized water (500 ml) at 25 to 30 0C. The mixture was stirred for 30 minutes. The precipitated solid was filtered, washed with water (10x 50ml) and dried at 45 to 50 0C under vacuum to obtain 8g of pure title compound as a crystalline solid having purity of 99.62% by HPLC. Example 11: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium (2.0 g) was dissolved in tetrahydrofuran (20 ml) and filtered to remove undissolved and suspended particles. The solvent was then evaporated under vacuum to obtain a powder which was then dried under vacuum at 40-600C to obtain 1.70 g of the title compound. Example 12: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium (2.0 g) was dissolved in dichloromethane (30 ml) and filtered to remove undissolved and suspended particles. The solvent was then evaporated under vacuum to obtain a powder which was then dried under vacuum at 40-600C to obtain 1.64 g of the title compound. Example 13: Preparation of amorphous mitiglinide calcium

Mitiglinide (2.0 g) was dissolved in methanol (20 ml) and methanolic ammonia (5.0 ml) solution was added to it. The solution was stirred at 25-30 0C and calcium chloride (1.5 g) dissolved in methanol was mixed with the solution of mitiglinide and ammonia in methanol and the solution was filtered to remove the suspended particles. The solvent was then evaporated under vacuum to obtain a powder which was then dried under vacuum at 40-600C to obtain 1.9 g of the title compound. Example 14: Preparation of amorphous mitiglinide calcium

Mitiglinide (2.0 g) was dissolved in dichloromethane (20 ml) and aqueous ammonia (3.6 ml, 25 % solution) was added to it. The solution was stirred at 25-300C and solid calcium chloride (1.5 g) was mixed with the solution of mitiglinide and ammonia in dichloromethane and the solution warmed at 30 – 35 0C. The solution was washed with water (2 xlO ml) and the clear solution was dried over sodium sulfate, filtered and evaporated under vacuum and finally dried at under vacuum at 40-60 0C to obtain 1.75 g of the title compound.

Example 15: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium dihydrate (2.0 g) was dissolved in ethyl acetate (30 ml) and filtered to remove undissolved and suspended particles. Approimately. 60 % of the solvent was distilled off under vacuum to obtain a stirrable solution. The solution was then cooled to 15-2O0C, mixed with n-heptane (20 ml) and the mixture was stirred for 30 minutes. The resulting solid was filtered, washed with n-heptane and dried under vacuum at 45-600C to yield 1.72 g of the title compound. Example 16: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium (2.Og) was dissolved in dichloromethane (30 ml) and filtered to remove undissolved and suspended particles. Approximately 60 % of the solvent was distilled off under vacuum to obtain a stirrable solution. The solution was then cooled to 15-200C and mixed with diisopropyl ether (20 ml). The mixture was stirred for 30 minutes and the resulting solid was filtered, washed with diisopropyl ether and dried under vacuum at 45-600C to obtain 1.70 g of the title compound. Example 17: Preparation of amorphous mitiglinide calcium

Mitiglinide (2.0 g) was dissolved in dichloromethane (20 ml) and aqueous ammonia (3.6 ml, 25 % solution) solution was added to it. The solution was stirred at 25-30 0C and mixed with solid calcium chloride (1.5 g) and the solution warmed at 30-35 0C and stirred for 30 minutes. The solution was washed with water (2 x 10 ml) and the clear solution was dried over sodium sulfate, and filtered. Approximately 60% of the solvent was distilled off under vacuum and the resulting viscous oil was cooled to 10-15 0C and mixed with diisopropyl ether (50 ml). The reaction mixture was stirred for 30-35 minutes and the resulting solid was filtered and dried at 40-600C to obtain 1.75 g of the title compound. Example 18: Conversion of amorphous mitiglinide calcium into crystalline mitiglinide calcium A suspension of amorphous mitiglinide calcium in diisopropyl ether (30 ml) was stirred for 2 hours at 25- 300C, filtered and dried under vacuum at 45-600C to obtain crystalline form of mitiglinide calcium. Example 19: Preparation of crystalline mitiglinide calcium

To a solution of mitiglinide (2.5 g) in water (2.5 ml), aqueous ammonia solution (approx 25%, 4.0 ml) and acetonitrile (2.5 ml) at 10-150C, calcium chloride (1.32 g) dissolved in demineralized water (15 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 25 ml) and acetone (2 x 5 ml) and dried at 45-500C under vacuum to obtain 2.12 g of title compound having purity: 99.72 % by HPLC.

Example 20: Preparation of crystalline mitiglinide calcium

To a solution of mitiglinide (2.5 g) in water (2.5 ml), aqueous ammonia solution (approx 25%, 4.0 ml) and tetrahydrofuran (2.5 ml) at 10-150C, calcium chloride (1.32 g) dissolved in demineralized water (15 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 25 ml) and acetone (2 x 5 ml) and dried at 45-500C under vacuum to obtain 1.95 g of title compound having purity: 99.52 % by HPLC.

Example 21; Preparation of crystalline mitiglinide calcium

To a solution of mitiglinide (30.0 g) in water (300 ml), aqueous ammonia solution (approx 25%, 48 ml) and acetone (300 ml) at 10-150C, calcium chloride (15.8 g) dissolved in demineralized water (180 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 300 ml) and acetone (2 x 60 ml) and dried at 45-500C under vacuum to obtain 24.32 g of title compound having purity: 99.42 % by HPLC.

(18 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 30 ml) and acetone (2 x 6 ml) and dried at 45-500C under vacuum to obtain 1.92 g of title compound having purity: 99.65 % by HPLC.

To a solution of (2S)-2-benzyl-l-((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)- butane-l,4-dione (20.0 g) in tetrahydrofuran (140 ml), a solution of lithium hydroxide monohydrate

(3.43 g,) in demineralized water (40 ml) was added and the reaction mixture was refluxed for 4 hours till the completion of the reactions (monitored by thin layer chromatography). After the completion of the reaction, the reaction mixture was poured into demineralized water (100 ml) and extracted with ethyl acetate (2 x 80 ml). The combined organic layer was washed with water (80 ml) and dried over sodium sulphate. The solvent was evaporated under reduced pressure to give residue which was stirred in isopropyl alcohol at 0-5 0C for 5 hours. The mixture was filtered and then dried at 40-45 0C under vacuum to obtain 12.48 g of title compound having purity 99.77 % by HPLC. Melting point = 77 – 800C.

(S)-Mitiglinide calcium dihydrate (1), calcium (2S)-2- benzyl-4-[(3aR,7aS)-octahydro-2H-isoindol-2-yl]-4- oxobutanoate hydrate (1:2:2), a novel hypoglycemic agent with a chemical structure different from that of the sulfonylureas. Mitiglinide inhibits the ATP-sensitive potassium channels in pancreatic β-cells and stimulates insulin release. The configuration of the stereogenic C-atom in the succinyl moiety is very important for the activity of compound and the absolute (S)- configuration is necessary for insulin secretory effect1-5. It is useful for the treatment of type-2 diabetes. (S)-Mitiglinide calcium dihydrate is designated chemically as calcium (2S)-2-benzyl-4-[(3aR,7aS)-octahydro-2Hisoindol-2-yl]-4-oxobutanoate hydrate (1:2:2). Its literature synthesis6 (Scheme-I) involves dehydration of (S)-2-benzylsuccinic acid (2) with acetic anhydride in the presence of dichloromethane gives corresponding anhydride (3). Reaction of (3) with cis-octahydroisondole (8) in presence of toluene affords (S)-mitiglinide (4) which on treatment with anhydrous calcium chloride in presence of sodium hydroxide and water gives (S)-mitiglinide calcium dihydrate (1).

(S)-Mitiglinde calcium dihydrate 1 synthesized is shown in Scheme-I. Dehydration of (S)-2-benzylsuccinic acid 2 with acetic anhydride gives corresponding (S)-Benzylsuccinic anhydride 3. The reaction of 3 with cis-octahydroisoindole 8 in the presence of toluene gives (S)-mitiglinide 4, which upon treatment with anhydrous calcium chloride in presence of sodium hydroxide and water afforded (S)-mitiglinide calcium dihydrate 1.

Mitiglinide calcium (mitiglinide calcium), the chemical name (2S) -2_ benzyl-3- (cis – hexahydro-2-isoindoline-carbonyl) propionic acid calcium salt dihydrate , for the treatment of type II diabetes.Kissei by Japanese pharmaceutical company research and development, and for the first time on sale in Japan in May 2004.Mitiglinide calcium is the second repaglinide, nateglinide after the first three columns MAG urea drugs, are ATP-dependent potassium channel blocker, is a derivative of phenylalanine, and its mechanism Similar sulfonylureas, but a faster onset of action and short half-life, is conducive to reducing postprandial blood glucose in diabetic patients, and avoid continuous glucose-induced low blood sugar, with the “in vitro pancreas” reputation.

郑德强 etc. on “Food and Drug” magazine was first disclosed the synthesis of calcium Mitiglinide, this method dimethyl succinate and benzaldehyde for raw materials, Stobble condensation, hydrolysis, dehydration anhydride, cis – perhydro isoindole reduced to give racemic acid after condensation, and then split, and salt get Mitiglinide calcium.Specific synthetic route the following equation.The method is relatively complex, in the preparation process to generate half of the unwanted enantiomer, which will waste a lot of cis – perhydro isoindole, and in the preparation of cis – to use science as a whole hydride hydrogen isoindole time reducing agent, the operation is more complicated, the cost is relatively high, and the chiral amine as a resolving agent split, the yield is low.

The present invention solves is to overcome the existing routes that exist in step lengthy reagent variety, low yield, long cycle, high cost, not suitable for industrial production shortcomings.The present invention provides the following formula preparation process route mitiglinide calcium, organic solvent for this preparation method uses less synthesis process is simple, high yield, good purity, suitable for industrial production.

Intermediate 1, methanol, and Ru (OAc) 2 [(S) -BINAP] into the reactor, the reactor with N2 the replacement air after heating to 50 ° C, a hydrogen pressure through 10h, cooled, filtered, The filtrate was concentrated to dryness to give the title intermediate 2.Step 3: 2- (S) – benzyl-4-oxo – (cis – perhydro isoindol-2-yl) butyric acid

Ethyl acetate was added to the reactor, triethylamine, imidazole and Intermediate 2, was stirred and cooled to -15~-5 ° C, was added dropwise thionyl chloride addition was complete, the -15 ° C~_5 ° C Under continued stirring 6h, a solution of cis – perhydro isoindole, drip completed, stirred at room temperature overnight, the reaction mixture was added IN hydrochloric acid, stirred Ih, separation, and the organic layer was washed with sodium hydroxide solution to extract IN The combined aqueous layer was washed with a small amount of ethyl acetate, the aqueous layer was adjusted with IN hydrochloric acid and the PH = 3, the aqueous layer was extracted with ethyl acetate, the organic layers combined, washed with water and saturated brine, and the organic layer was dried over anhydrous Na2SO4, filtered and the filtrate concentrated under reduced pressure to obtain the objective compound 3 billion Step 4: Preparation of calcium Mitiglinide

The 3 was dissolved in ethanol, was added 2N sodium hydroxide solution, after mixing the solution was added dropwise a 10% aqueous solution of calcium chloride, the reaction mixture was stirred vigorously 3~5h, ice-cooled, filtered, the filter cake with 95% ethanol beating crystallization, filtration, and dried in vacuo to give the title compound I.

Accordingly, the present invention is a method for preparing mitiglinide calcium has the following advantages:

1, Step 1, using commercially available sodium methylate (sodium ethanol) instead of sodium block as a proton agent, effectively avoid the risk of sodium block formed during the reaction a lot of flammable hydrogen gas, industrial production safer.Another use dropping protonated reagent feeding method can effectively avoid succinic acid alkyl ester of two methylene groups are protonated and reduce the incidence of side effects, so that the yield increased by nearly 20%.

2, Step 2, the selective reduction of chiral reagent (S) -BINAP instead of the original route after the first split reduction method, not only simplifies the reaction step, but low yield while avoiding split It leads to the risk of an increase in cost.

3, Step 3, the fixed selective amidation reaction conditions instead of the original first into anhydride after amidation reaction that simplifies the reaction steps to reduce the unit operations, shortening the production cycle, improve production efficiency.

Mitiglinide calcium Phenylalanine belong chiral compound synthesis routes according to different methods of constructing chiral center has the following three synthetic process:

① split method😦 Document: CN 102101838A, CN 1844096, etc.)

In this method, diethyl succinate and benzaldehyde by Mobbe condensation, hydrolysis, dehydration anhydride, and after cis-hydrogenated isoindole condensation is reduced to give racemic acid, and then split, and salt to give Mitiglinide calcium.The first method step condensation reaction impurities, product separation and purification difficult, finally resolving the yield is low.This method is also a lack atom economy.

[0027] This method requires expensive rhodium complexes (Rh, (2S, 4Q-N_-butoxycarbonyl-4-diphenylphosphino _2_ diphenylphosphino-2-diphenylphosphino methylpyrrolidine alkyl), making the production cost is greatly improved, and the need for high-pressure hydrogenation reaction, is not conducive to industrial production.

2-hydroxyphenyl propionic acid in an organic base such as triethylamine or pyridine, or an inorganic base such as sodium bicarbonate, sodium carbonate or potassium carbonate effect, p-hydroxybenzoic acid ester protecting performed, the protecting group used is an aliphatic or aromatic sulfonic acid group such as mesylate, tosylate or p-toluenesulfonic acid group, a sulfonic acid group is preferably methyl group or p-toluenesulfonic acid.

Ethyl mitiglinide under basic conditions such as sodium hydroxide, potassium hydroxide, or an amine (ammonia) in the presence of an aqueous solution of calcium chloride, and hydrolyzed as calcium salt, in aqueous solution under conditions of heavy alcohol crystallization, high purity mitiglinide calcium.

The present invention and the prior art comparison, has the following advantages:

1, to find an innovative high-yield process for preparing calcium Mitiglinide route, a total yield of 47%;

2, with respect to the routing methods reported in the literature, the optical yield doubled, ee greater than 99%;

3. The process route of the raw materials are cheap, readily available, avoiding costly chiral resolving agents or the use of a catalyst;

In the present invention, (D) – phenylalanine as a starting material, after diazotization, a hydroxyl group and a carboxyl group protected, nucleophilic substitution, hydrolysis and other reactions prepared mitiglinide calcium, high yield.The present invention provides a process used by a wide range of raw materials, low prices, the total yield of 47%, optical purity greater than 99%, and mild reaction conditions, the reaction process is simple, avoid the literature, such as split, high-pressure hydrogenation method low yield, long reaction steps and other shortcomings, but also to overcome the harsh conditions of high temperature reaction deacidification, etc. for preparation and production of calcium Mitiglinide provides a new choice.

In the present invention, (D) – phenylalanine as a starting material, after diazotization, a hydroxyl group and a carboxyl group protected, nucleophilic substitution, hydrolysis and other reactions prepared mitiglinide calcium, high yield.The present invention provides a process used by a wide range of raw materials, low prices, the total yield of 47%, optical purity greater than 99%, and mild reaction conditions, the reaction process is simple, avoid the literature, such as split, high-pressure hydrogenation method low yield, long reaction steps and other shortcomings for Mitiglinide calcium preparation and production of a new choice.

Preferably, in the above embodiment, each step may be the following alternative, the embodiment can achieve the same advantageous effects to a third embodiment of embodiment:

2-hydroxyphenyl propionic acid in an organic base such as triethylamine or pyridine, or an inorganic base such as sodium bicarbonate, sodium carbonate or potassium carbonate effect, p-hydroxybenzoic acid ester protecting performed, the protecting group used is an aliphatic or aromatic sulfonic acid group such as mesylate, tosylate or p-toluenesulfonic acid group, a sulfonic acid group is preferably methyl group or p-toluenesulfonic acid.

Ethyl mitiglinide under basic conditions such as sodium hydroxide, potassium hydroxide, or an amine (ammonia) in the presence of an aqueous solution of calcium chloride, and hydrolyzed as calcium salt, in aqueous solution under conditions of heavy alcohol crystallization, high purity mitiglinide calcium.

Mitiglinide Calcium is synthesized by Japan Orange Health Pharmaceutical Co., Ltd., in April 2004 in Japan, for through diet and exercise therapy can effectively control high blood sugar in type II diabetes patients.Mitiglinide calcium is the second repaglinide, nateglinide third after the United States and Glenn urea drugs belong phenylalanine derivatives.By closing ΑΤΡ Mitiglinide calcium-dependent pancreatic β cell membrane Κ channel, resulting in the Ca flow, increase intracellular Ca concentration of extracellular vesicles containing threshing leaving insulin, thereby stimulating the secretion of insulin.And only when the meal will be rapid and transient stimulates the pancreas to secrete insulin, sulphonylureas with the traditional Compared to the rapid onset and short duration of action, inhibition of postprandial hyperglycemia characteristic of type II diabetes, to avoid low blood sugar react, early first- and mild diabetes treatment, and well tolerated.

According to the literature and patent reports, prepared Mitiglinide calcium are the following methods.

Abstract: A novel convenient synthesis of the hypoglycemic agent mitiglinide was developed. (2S)-4-[(3aR,7aS)-Octahydro-2H-isoindol-2-yl]-4-oxo-2-benzyl-butanoic acid (6) was prepared by selective hydrolysis of ethyl 4-[(3aR,7aS)-octahydro-2Hisoindol-2-yl]-4-oxo-2-benzyl-butanoate (5) using a-chymotrypsin; the latter was prepared by a novel facile route from (3aR,7aS)-octahydro-2H-isoindole. The overall yield was 25.6%.

Keywords: a-chymotrypsin, mitiglinide, synthesis

Mitiglinide (calcium bis[(2S)-4-[(3aR,7aS)-octahydro-2H–isoindol-2-yl]-4oxo-2-benzylbutanoate]dihydrate) is a novel oral hypoglycemic agent. It inhibits the adenosine triphosphate (ATP)-sensitive potassium channels in pancreatic b-cells and stimulates insulin release like sulfonylureas,[1] but has a rapid onset and short-lasting hypoglycemic effect as compared with the latter.

Mitiglinide has been synthesized by several related methods that involve optical resolution,[2] asymmetric synthesis,[2a,3] and diasteroselective alkylation using chiral auxiliary.[4]

In a previous article,[2] two optical resolution methods of the key compound racemic acid 4 were reported. One of them involves esterification with optically active alcohols, which are separated into the diastereomers by column chromatogeaphy and hydrolyzed. Only the diastereomeric (S)-Nbenzyl mandelamide ester could be separated; the overall yield was 28%,

The alternative method was optical resolution by optically active bases. The best result was 30.8% yield and 97% ee when using (R)-1-(1-naphthyl)-ethylamine as a base. In this article, we have developed a new optical resolution method of racemic ester 5 by a-chymotrypsin in 45.3% yield; the optical purity of (S)-acid (6) determined by chiral-phase high performance liquid chromatography (HPLC) on Sumichiral

OA3300 was 99.2% ee, and, the method can be used for scale-up preparation.

The synthesis of free acid 6 is shown in Scheme 1. (3aR,7aS)-Octahydro2H-isoindole was chloroacetylated in the presence of Et3N to afford (3aR, 7aS)-2-(chloro-acetyl)-octahydro-2H-isoindole (2), which was condensed with diethyl benzylmalonate followed by hydrolysis and decarbonylation to obtain 4-[(3aR,7aS)-octahydro-2H-isoindol-2-yl]-4-oxo-2-benzyl-butanoic acid (4). The overall yield of the three-step synthesis was 62.9%. The racemic acid (4) was esterified with SOCl2/EtOH to give the corresponding racemic ester (5). The (R)-ester was selectively hydrolyzed by a-chymotrypsin to separate out the (S)-ester, which was subjected to hydrolysis, giving 6.

The overall yield was 28.5% [based on (3aR,7aS)-octahydro-2H-isoindole].

Compound 6 was treated with calcium chloride and 25% ammonium hydroxide to give mitiglinide; after recrystallization from 95% EtOH, the pure product was obtained in 90% yield.

Example 1: Preparation of (R) 4-benzyl-3-(3-phenylpropionv0-oxazolidin-2-one To a solution of (R)-4-benzyloxazolidin-2-one (50 g), 4-dimethylaminopyridine (4.85 g), 3-phenyl propionic acid (55.08 g) in dichloromethane (375 ml) under nitrogen atmosphere at 0-5 0C, dicyclohexylcarbodiimide (975.65 g) was added. The temperature was slowly raised to 25-30 0C and stirring was continued until no starting material was left as was confirmed by thin layer chromatography. Dicyclohexylurea formed during the reaction was filtered, washed with dichloromethane (200 ml) and the filtrate was washed with saturated solution of sodium bicarbonate (500 ml). The solution was dried over sodium sulphate and solvent was distilled off to obtained crude product which was purified from methanol (200 ml) at 10-15 °C and washed with methanol (50 ml) to obtain 81.0 g of the title compound. Example 2: Preparation of 3(5)-benzyl-4-(4-(J?)-benzyl-2-oxo-oxazolidin-3-yl)-4-oxo-butyrϊc acid tert-butyl ester

To a solution of (/?)-4-benzyl-3-(3-phenyl-propionyl)-oxazolidin-2-one (150 g) in anhydrous tetrahydrofuran (1.5 It) was added a solution of sodium hexamethyldisilazane (462 ml, 36-38% solution in tetrahydrofuran) with stirring at -85 to -95 0C for 60 minutes. Tert-butyl bromo acetate (137.5 g) in tetrahydrofuran (300 ml) was added to reaction mass and then stirred to 60 minutes at -85 to -95 0C. After completion of the reaction (monitored by TLC), the reaction mixture was poured into ammonium chloride solution (10%, 2.0 It) and extracted with ethyl acetate (2×750 ml). The combined organic layer was washed with demineralized water (1×750 ml) and dried over sodium sulphate. The solvent was evaporated under reduced pressure to obtain oily residue which was stirred with mixture of n-hexane (100 ml) and isopropyl alcohol (100 ml) at Oto -50C, filtered and dried under vacuum to obtain 153.12 g of title compound having chemical purity 99.41%, chiral purity 99.91% by HPLC, [α]D20: (-)97.52° (c = 1, CHCl3) and M.P. : 117.1-118.20C.

Example 3: Preparation of 3(5)-benzyl-4-(4(i?)-benzyl-2-oxo-oxazolidin-3-yl)-4-oxobutyric acid Trifluoroacetic acid (100 g) was added to a solution of 3(5)-benzyl-4-(4-(/?)-benzyl-2-oxo-oxazolidin-3- yl)-4-oxobutyric acid tert-butyl ester (100 g) in dichloromethane (700 ml) at 25 0C and mixture was stirred further for about 12 hours ( when TLC indicated reaction to be complete). The reaction mixture was poured in to ammonium chloride solution (10%, 500 ml). The dichloromethane layer was separated and aqueous layer was extracted with dichloromethane (2 x 250 ml). The combined organic layer was dried over sodium sulphate and evaporated under reduced pressure to obtain title compound. The crude product was recrystallized from a mixture of ethyl acetate: n-hexane (1:4, 500 ml) to obtain 78.75g of the title compound having purity 99.56% by HPLC and M.P.: 145.9-146.40C.

To a solution of 3(5)-benzyl-4-(4-(/?)-benzyl-2-oxo-oxazolidin-3-yl)-4-oxo-butyric acid (50 g) in anhydrous dichloromethane (1.25 It) was added triethylamine (50 ml) with stirring at -20 to -30 0C and the stirred for 15 minutes. A solution of isobutylchloroformate (37.50g) in anhydrous dichloromethane (50 ml) was added at -20 to -30 0C and stirred for 60 minutes. Thereafter, a solution of cis- hexahydroisoindoline (32.50 g) in anhydrous dichloromethane (50 ml) was slowly added by maintaining temperature -20 to -300C. After the completion of the reaction (monitored by HPLC), the mixture was successively washed with 0.5N hydrochloric acid solution (500 ml), brine (300 ml) and dried over sodium sulphate. The solvent was evaporated under reduced pressure to obtain 102.0 g of the title compound having purity 94.39% by HPLC.

To the crude (2S)-2-benzyl-l-((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)- butane- 1,4-dione (51.0 g) was added methanol (150 ml) and the mixture was stirred for 5 hours at 0 to 5 0C. Solid that precipitated out was filtered, slurry washed with cold methanol (25 ml) and dried at 45 -50 0C under vacuum to obtain 28.80 g of pure title compound as a crystalline solid having purity of 99.71% by HPLC and M. P.: 104.1-105.70C.

(2S)-2-Benzyl- 1 -((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)-butane- 1 ,4-dione (28.0 g) was dissolved in tetrahydrofuran (196 ml) and a mixture of lithium hydroxide monohydrate (3.51 g) in demineralized water (56 ml) and hydrogen peroxide (40% solution, 5.5 ml) was added with stirring at 0 to 5 0C over a period of 30 minutes. The reaction mixture was further stirred at 0 to 5 0C till the completion of the reaction. After the completion of the reaction (monitored by TLC), the reaction was quenched with the addition of cooled sodium meta-bisulphate solution (25%, 168 ml) at 0 to 10 0C. The reaction mixture was extracted with ethyl acetate (2×112 ml), the layers were separated and the aqueous layer was discarded. The HPLC analysis of the aqueous layer shows 0.77% of amide impurity. The ethyl acetate layer was then extracted with aqueous ammonia solution (4%, 2×40 ml). The layers were separated and the aqueous layer was further extracted with ethyl acetate (2×280 ml). Combined ethyl acetate layer was discarded. This aqueous layer (280 ml) was used as such in the next stage. The aqueous layer display purity 96.19 % by HPLC and amide impurity 0.04% by HPLC. Step-2: Preparation of calcium salt of dSVmitiglinide

To the above stirred solution of (S)-mitiglinide in water and ammonia(280 ml), methanol (168 ml) was added, followed by calcium chloride (4.48 g) dissolved in demineralized water (56 ml) at ambient temperature and the mixture was stirred for 2 hours. The resulting precipitate was filtered, successively slurry washed with water (3 x 140 ml) and acetone (2 x 70 ml) and dried at 450C -500C under vacuum to obtain 16.1 g of title compound having purity 99.67% by HPLC and amide impurity 0.01% by HPLC. The title product was re-precipitated from a mixture of methanol and water and dried to obtain pure title compound.

Example 7: Preparation of (.SVmitiglinide

To a solution of (2S)-2-benzyl-l-((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)- butane- 1,4-dione (50 g) in tetrahydrofuran (350 ml) was added a solution of lithium hydroxide monohydrate (8.65 g) in demineralized water (100 ml) and hydrogen peroxide (30% w/w, 40 ml) with stirring at 5 to 10 0C over a period of 15 minutes. After the completion of reaction, sodium meta- bisulphate solution (40%, 500 ml) was added to the reaction mixture and the mixture was extracted with ethyl acetate (2 x 250 ml). The organic layer was dried over sodium sulphate and evaporated under vacuum to obtain 45.5 g of title compound having 35 % of R-benzyl oxozolidin-2-one as impurity. Example 8: Purification of (.S)-mitiglinide

Aqueous ammonia solution (4%, 300 ml) was added to the crude (5)-mitiglinide (30 g) and stirred. The reaction mixture was washed with ethyl acetate (3 x 300 ml). Thereafter the reaction mixture was acidified to pH 1 to 2 with IN hydrochloric acid solution (250 ml) and extracted with ethyl acetate (2 x 150 ml). The layers were separated and ethyl acetate layer was washed with demineralized water (2 x 150 ml), dried over sodium sulphate and then evaporated under reduced pressure to obtain 16.2 g of pure (5)-mitiglinide having purity 95.55% by HPLC Example 9: Preparation of calcium salt of (S)-mitiglinide

To a solution of (<S)-mitiglinide (15 g) in water (150 ml) and aqueous ammonia solution (25%, 15 ml) at 25 to 30 0C, a solution of calcium chloride (7.5 g) in demineralized water (37.5 ml) was added. The mixture was stirred for 1 hour to precipitate the calcium salt of (5)-mitiglinide dihydrate. The resulting precipitate was filtered, slurry washed with water (3 x 150ml) and dried at 45 to 50 0C to obtain 13.25 g of the title compound having purity of 98.84% by HPLC. Example 10: Purification of calcium salt of (5)-mitiglinide

(iS)-mitiglinide calcium (10 g) was dissolved in dimethylformamide (100 ml). This is followed by the addition of demineralized water (500 ml) at 25 to 30 0C. The mixture was stirred for 30 minutes. The precipitated solid was filtered, washed with water (10x 50ml) and dried at 45 to 50 0C under vacuum to obtain 8g of pure title compound as a crystalline solid having purity of 99.62% by HPLC. Example 11: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium (2.0 g) was dissolved in tetrahydrofuran (20 ml) and filtered to remove undissolved and suspended particles. The solvent was then evaporated under vacuum to obtain a powder which was then dried under vacuum at 40-600C to obtain 1.70 g of the title compound. Example 12: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium (2.0 g) was dissolved in dichloromethane (30 ml) and filtered to remove undissolved and suspended particles. The solvent was then evaporated under vacuum to obtain a powder which was then dried under vacuum at 40-600C to obtain 1.64 g of the title compound. Example 13: Preparation of amorphous mitiglinide calcium

Mitiglinide (2.0 g) was dissolved in methanol (20 ml) and methanolic ammonia (5.0 ml) solution was added to it. The solution was stirred at 25-30 0C and calcium chloride (1.5 g) dissolved in methanol was mixed with the solution of mitiglinide and ammonia in methanol and the solution was filtered to remove the suspended particles. The solvent was then evaporated under vacuum to obtain a powder which was then dried under vacuum at 40-600C to obtain 1.9 g of the title compound. Example 14: Preparation of amorphous mitiglinide calcium

Mitiglinide (2.0 g) was dissolved in dichloromethane (20 ml) and aqueous ammonia (3.6 ml, 25 % solution) was added to it. The solution was stirred at 25-300C and solid calcium chloride (1.5 g) was mixed with the solution of mitiglinide and ammonia in dichloromethane and the solution warmed at 30 – 35 0C. The solution was washed with water (2 xlO ml) and the clear solution was dried over sodium sulfate, filtered and evaporated under vacuum and finally dried at under vacuum at 40-60 0C to obtain 1.75 g of the title compound.

Example 15: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium dihydrate (2.0 g) was dissolved in ethyl acetate (30 ml) and filtered to remove undissolved and suspended particles. Approimately. 60 % of the solvent was distilled off under vacuum to obtain a stirrable solution. The solution was then cooled to 15-2O0C, mixed with n-heptane (20 ml) and the mixture was stirred for 30 minutes. The resulting solid was filtered, washed with n-heptane and dried under vacuum at 45-600C to yield 1.72 g of the title compound. Example 16: Preparation of amorphous mitiglinide calcium

Crystalline mitiglinide calcium (2.Og) was dissolved in dichloromethane (30 ml) and filtered to remove undissolved and suspended particles. Approximately 60 % of the solvent was distilled off under vacuum to obtain a stirrable solution. The solution was then cooled to 15-200C and mixed with diisopropyl ether (20 ml). The mixture was stirred for 30 minutes and the resulting solid was filtered, washed with diisopropyl ether and dried under vacuum at 45-600C to obtain 1.70 g of the title compound. Example 17: Preparation of amorphous mitiglinide calcium

Mitiglinide (2.0 g) was dissolved in dichloromethane (20 ml) and aqueous ammonia (3.6 ml, 25 % solution) solution was added to it. The solution was stirred at 25-30 0C and mixed with solid calcium chloride (1.5 g) and the solution warmed at 30-35 0C and stirred for 30 minutes. The solution was washed with water (2 x 10 ml) and the clear solution was dried over sodium sulfate, and filtered. Approximately 60% of the solvent was distilled off under vacuum and the resulting viscous oil was cooled to 10-15 0C and mixed with diisopropyl ether (50 ml). The reaction mixture was stirred for 30-35 minutes and the resulting solid was filtered and dried at 40-600C to obtain 1.75 g of the title compound. Example 18: Conversion of amorphous mitiglinide calcium into crystalline mitiglinide calcium A suspension of amorphous mitiglinide calcium in diisopropyl ether (30 ml) was stirred for 2 hours at 25- 300C, filtered and dried under vacuum at 45-600C to obtain crystalline form of mitiglinide calcium. Example 19: Preparation of crystalline mitiglinide calcium

To a solution of mitiglinide (2.5 g) in water (2.5 ml), aqueous ammonia solution (approx 25%, 4.0 ml) and acetonitrile (2.5 ml) at 10-150C, calcium chloride (1.32 g) dissolved in demineralized water (15 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 25 ml) and acetone (2 x 5 ml) and dried at 45-500C under vacuum to obtain 2.12 g of title compound having purity: 99.72 % by HPLC.

Example 20: Preparation of crystalline mitiglinide calcium

To a solution of mitiglinide (2.5 g) in water (2.5 ml), aqueous ammonia solution (approx 25%, 4.0 ml) and tetrahydrofuran (2.5 ml) at 10-150C, calcium chloride (1.32 g) dissolved in demineralized water (15 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 25 ml) and acetone (2 x 5 ml) and dried at 45-500C under vacuum to obtain 1.95 g of title compound having purity: 99.52 % by HPLC.

Example 21; Preparation of crystalline mitiglinide calcium

To a solution of mitiglinide (30.0 g) in water (300 ml), aqueous ammonia solution (approx 25%, 48 ml) and acetone (300 ml) at 10-150C, calcium chloride (15.8 g) dissolved in demineralized water (180 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 300 ml) and acetone (2 x 60 ml) and dried at 45-500C under vacuum to obtain 24.32 g of title compound having purity: 99.42 % by HPLC.

(18 ml) was added. The mixture was stirred for 2 hours. The resulting precipitate was filtered, slurry washed with water (3 x 30 ml) and acetone (2 x 6 ml) and dried at 45-500C under vacuum to obtain 1.92 g of title compound having purity: 99.65 % by HPLC.

To a solution of (2S)-2-benzyl-l-((4R)-4-benzyl-2-oxo-oxazolidin-3-yl)-4-(hexahydro-isoindolin-2-yl)- butane-l,4-dione (20.0 g) in tetrahydrofuran (140 ml), a solution of lithium hydroxide monohydrate

(3.43 g,) in demineralized water (40 ml) was added and the reaction mixture was refluxed for 4 hours till the completion of the reactions (monitored by thin layer chromatography). After the completion of the reaction, the reaction mixture was poured into demineralized water (100 ml) and extracted with ethyl acetate (2 x 80 ml). The combined organic layer was washed with water (80 ml) and dried over sodium sulphate. The solvent was evaporated under reduced pressure to give residue which was stirred in isopropyl alcohol at 0-5 0C for 5 hours. The mixture was filtered and then dried at 40-45 0C under vacuum to obtain 12.48 g of title compound having purity 99.77 % by HPLC. Melting point = 77 – 800C.

Mitiglinide calcium (mitiglinide calcium), the chemical name (2S) _2_ benzyl _3_ (cis – hexahydro _2_ isoindolinyl-carbonyl) propionate dihydrate by Japanese pharmaceutical company developed Kissei ATP-dependent potassium channel blockers, 2004 for the first time in Japan for the treatment of type II diabetes.

Mitiglinide calcium is the second repaglinide, nateglinide after the first three columns MAG urea drugs, is a derivative of phenylalanine, which acts like mechanism sulfonylurea, but faster onset and the short half-life, is conducive to reducing postprandial blood glucose in diabetic patients, but also to avoid low blood sugar caused by continuous glucose, with “in vitro pancreas” reputation.

The process for the preparation of KAD-1229 starts from ()-camphorsultam ((3aS)-8,8-dimethylhexahydro-3a,6-methano-2,1-benzisothiazole 2,2-dioxide), readily available in 85% yield from ()- -camphor [4]. Treatment of ()-camphorsultam with excess 3-phenylpropionyl chloride in the presence of NaH in toluene at room temperature gave 1 in 91% yield (Scheme) [5]. An alternative procedure is to reflux camphorsultam with 1.1 to ca. 1.5 equiv. of 3-phenylpropionyl chloride in MeCN for 8 ± 10 h [6]. The crude product, acylsultam 1, purified by recrystallization from EtOH/H2O in 89% yield, was reacted with an equimolar amount of base to form the chiral enolate in dry ice/EtOH bath, followed by C()-re-alkylation [7] with tert-butyl bromoacetate to give 2. The choice of the organic base was very important: the reaction with BuLi, lithium diisopropylamide (LDA), or NaHMD (sodium hexamethyldisilazane) gave 2 in 30 ± 40%, 60%, or 90% yield, respectively, after recrystallization from MeOH. Alkylation promoted by these bases tends to give products with high diastereoselectivity, and the diastereoisomeric purity of crude product 2 was determined to be 93%. However, the reaction with NaHMDS as the base proceeded smoothly in high yield. The tert-butyl ester 2 was cleaved with TFA (CF3COOH) in CH2Cl2 to give the free acid 3 in 87% yield [8]. Acylation of (3aR,7aS)-octahydro-1H-isoindole with 3 by a mixed anhydride method afforded 4 in 84% yield [9]. Compound 4 can be also obtained in 85% yield via direct alkylation of 1 with (3aR,7aS)-2-(bromoacetyl)octahydro-1H-isoindole; however, the yield of the (2-bromoacetyl)octahydro-1H-isoindole prepared from 2-bromoacetyl bromide and cis-octahydro-1H-isoindole was only 40%. Nondestructive cleavage of 4 by hydroperoxide-assisted saponification (LiOH, aq. H2O2 , THF, r.t.) regenerated the camphorsultam (96% recovered yield) and gave mitiglinide (5) in 93% yield and high enantiomeric excess ( 99% by HPLC analysis of the corresponding methyl ester) [7]. Product 5 was treated with 2 NaOH, followed by treatment with CaCl2 . Recrystallization from aqueous EtOH gave KAD-1229 in 91% yield, with a melting point and specific rotation data identical to those in the literature [2b]. Co

mitiglinide as a colorless viscous oil. The ee was determined to be 99.4% by HPLC analysis of the corresponding Me ester on a Chiralcel AS column (250 4.6 mm, flow rate 0.7 ml/min, UV 214 nm, n-hexane/i-PrOH 80 : 20 as the eluent).

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DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with GLENMARK PHARMACEUTICALS LTD, Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 29 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international,
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and implementation them on commercial scale over a 29 year tenure till date Aug 2016, Around 30 plus products in his career. He has good knowledge of IPM, GMP, Regulatory aspects, he has several International patents published worldwide . He has good proficiency in Technology transfer, Spectroscopy, Stereochemistry, Synthesis, Polymorphism etc., He suffered a paralytic stroke/ Acute Transverse mylitis in Dec 2007 and is 90 %Paralysed, He is bound to a wheelchair, this seems to have injected feul in him to help chemists all around the world, he is more active than before and is pushing boundaries, He has 9 million plus hits on Google, 2.5 lakh plus connections on all networking sites, 25 Lakh plus views on dozen plus blogs, He makes himself available to all, contact him on +91 9323115463, email amcrasto@gmail.com, Twitter, @amcrasto , He lives and will die for his family, 90% paralysis cannot kill his soul., Notably he has 13 lakh plus views on New Drug Approvals Blog in 212 countries......https://newdrugapprovals.wordpress.com/ , He appreciates the help he gets from one and all, Friends, Family, Glenmark, Readers, Wellwishers, Doctors, Drug authorities, His Contacts, Physiotherapist, etc

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